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SubjectRe: [PATCH] KVM: SVM: Don't intercept IRET when injecting NMI and vNMI is enabled
From
On Tue, Oct 10, 2023, Maxim Levitsky wrote:
> У пн, 2023-10-09 у 14:29 -0700, Sean Christopherson пише:
> > Note, per the APM, hardware sets the BLOCKING flag when software directly
> > directly injects an NMI:
> >
> > If Event Injection is used to inject an NMI when NMI Virtualization is
> > enabled, VMRUN sets V_NMI_MASK in the guest state.
>
> I think that this comment is not needed in the commit message. It describes
> a different unrelated concern and can be put somewhere in the code but
> not in the commit message.

I strongly disagree, this blurb in the APM directly affects the patch. If hardware
didn't set V_NMI_MASK, then the patch would need to be at least this:

--
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index b7472ad183b9..d34ee3b8293e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3569,8 +3569,12 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
if (svm->nmi_l1_to_l2)
return;

- svm->nmi_masked = true;
- svm_set_iret_intercept(svm);
+ if (is_vnmi_enabled(svm)) {
+ svm->vmcb->control.int_ctl |= V_NMI_BLOCKING_MASK;
+ } else {
+ svm->nmi_masked = true;
+ svm_set_iret_intercept(svm);
+ }
++vcpu->stat.nmi_injections;
}

base-commit: 86701e115030e020a052216baa942e8547e0b487
--

and maybe even more to deal with canceled injection.

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